In a computer network handling sensitive data, such as data in military or financial environments, portions of the network may be connected by one-way data links. The term “one-way link” is used in the context of the present patent application and in the claims to refer to a communication link that is physically configured to carry signals in one direction and to be incapable of carrying signals in the opposite direction. For example, confidential data that must not be accessed from external sites may be stored on a computer that is configured to receive data over a one-way link and has no physical outgoing link over which data might be transmitted to the external site.
One-way links may be implemented, for example, using Waterfall™ systems, which are manufactured by Gita Technologies, Ltd. (Rosh HaAyin, Israel). Specifications of Waterfall systems are available at www.waterfall.co.il. The Waterfall system provides a physical one-way connection based on fiberoptic communication, using an underlying proprietary transfer protocol. When a transmitting computer is connected by a Waterfall system (or other one-way link) to a receiving computer, the receiving computer can receive data from the transmitting computer but has no physical means of sending any return communications to the transmitting computer.
Supervisory Control And Data Acquisition (SCADA) systems are commonly deployed for purposes of data collection and, in some cases, control in a wide variety of different process environments. Typically, as the name implies, SCADA systems are used for supervisory purposes, and are not critical to real-time control of the process (which is generally carried out by a real-time automated control system, separate from the SCADA system). Common SCADA applications include monitoring and control of industrial processes, infrastructure operations, and facility conditions. Although the term “SCADA” is sometimes used to refer specifically to large-scale distributed monitoring and control systems, in the context of the present patent application this term denotes any sort of supervisory monitoring system that is separate from the facility or process being monitored. The term “facility” is used broadly herein to refer generally to any and all sorts of premises, equipment and apparatus that may be monitored by such a SCADA system. The term “process” is likewise defined broadly to refer to any sort of sequence of physical operations and/or events that produces an identifiable outcome.
Recently, there have been mounting concerns regarding the security of SCADA-based systems and the vulnerability of such systems to cyber-terrorism. Security vendors, such as Check Point® Software Technologies (Ramat Gan, Israel) and Innominate Security Technologies AG (Berlin, Germany), have begun to address these risks by developing lines of specialized industrial firewall and virtual private network (VPN) solutions for SCADA networks. In addition, the Multi-State Information Sharing and Analysis Center (www.msisac.org), with support from the U.S. Department of Homeland Security, has developed guidelines, known as the Cyber Security Procurement Language for Control Systems, for SCADA system security. These guidelines cover topics including the removal of unnecessary services and programs, minimum firewall requirements for perimeter security, and disabling or modifying guest and other well-known accounts.